Okay, I'm pretty sure about this one! I might be wrong but:
If the number is prime and LESS than 13 (so it can't be 13 either), it's either 2, 3, 5, 7, or 11. Those are 5 numbers in all, and 4 of those are odd. So the fraction would be 4/5!
I might have done this wrong, but I hope it helps!! Have a nice day c:
